Aquarium Outfitters in Wake Forest has a 20" clown knife you might like, and some other monster cats, cichlids, sleeper gudgeons, maybe arowanas. Big-G in Hickory is selling a pair of Amphilophus festae. And "fishspeaker" is unloading some tank-busters on the Charlotte (CAAS) forum. Stingrays are not good competitors against aggressive fish.
With an arowana,or a redtail cat ,You are going to deffinitely need a bigger tank,Say goodbye to the peacock bass,or the clown knife,When that redtail grows...You had better have a heavy hood,when that arowana goes airborn.....Just saying...That would be a great African cichlid tank,and think of all the colors,and less maintanaince and you could sell the offspring to pay for supplies..